How to Read the Parabolic SAR: Accelerating Trailing Dots and the Reversal Rule

What Parabolic SAR draws

Parabolic SAR (Parabolic Stop and Reverse) places one dot per bar below or above price to show both the current direction and the point at which that direction should be abandoned. Wilder, who created ADX, RSI and ATR, introduced it in the same book. While it reads bullish, the dots sit below price and follow it up; while it reads bearish, they sit above price and follow it down. The name means "stop and reverse": when price touches the dot, the current direction is stopped and flipped to the opposite one. So the indicator has no neutral state. It always points either up or down. "Parabolic" comes from the shape the dots trace. The longer a trend lasts, the faster the dots approach price, so on a chart they curve up or down like a parabola. What to look at on screen is which side of price the dots are on and how narrow the gap between dots and price has become. The narrower the gap, the smaller the counter-move needed for a reversal.

Definition and calculation: Wilder's formula

The core of the calculation is one line: the next bar's SAR equals the current SAR plus the acceleration factor × (extreme point − current SAR). The extreme point is the most extreme price since the current trend began: the highest high in an uptrend, the lowest low in a downtrend. In other words, the dot moves each bar toward the extreme point by a fixed fraction of the remaining distance. The acceleration factor starts small when a trend begins, grows by a set step each time a new extreme point is made, and stops at a set maximum. The common defaults, proposed by Wilder and also used by TradingView's built-in indicator, are a start of 0.02, a step of 0.02 and a maximum of 0.2. This site's reference calculation code does not include this indicator, so these values are presented here as common defaults. Below is the calculation order using an uptrend as the example; a downtrend is calculated the same way with up and down reversed.

• Next SAR = current SAR + acceleration factor × (extreme point − current SAR)
• When a new high is made, update the extreme point and raise the acceleration factor by 0.02 (up to 0.2)
• The next SAR may not be above the lows of the two previous bars (if it is, lower it to that low)
• When the low touches the SAR, reverse to a downtrend: the new SAR is the previous trend's extreme point, and the acceleration factor resets to 0.02

The acceleration factor: dots that close in over time

The defining feature of Parabolic SAR is that the dots follow price faster and faster. Early in a trend the acceleration factor is 0.02, so the dot moves only 2% of the remaining distance to the extreme point each bar and stays well away from price. Each new high raises the factor to 0.04, then 0.06, and at the 0.2 maximum the dot covers a fifth of the remaining distance every bar. This structure has one important property. Even if price fails to make new highs and just rests sideways, the dot keeps moving toward the extreme point. Unlike other trailing lines that follow only when price moves, Parabolic SAR narrows the gap simply as time passes. Wilder presented the indicator as one that uses time as well as price, and it is often explained as turning into a formula the idea that a trend that does not progress in time should be doubted. So a long pullback or range tends to let the dots reach price and trigger a reversal, which is also why the indicator is weak in sideways markets. A larger step or maximum makes the dots close in faster and flips more frequent; smaller values leave the dots farther away and reversals later.

The reversal rule: when the high or low touches

In Wilder's definition, reversals are judged by the bar's high and low, not the close. In an uptrend, the direction turns bearish when the bar's low touches or drops below the SAR; in a downtrend, it turns bullish when the high touches or rises above the SAR. A wick merely touching the dot is a reversal, which is a major difference from Supertrend, where the close must finish beyond the line. When a reversal happens, the first SAR of the new trend is placed at the previous trend's extreme point, that is, at the highest high if it flipped from up to down, and the acceleration factor returns to its starting value. So right after a reversal, the dot starts again far from price. There is also a limit that keeps the dot from passing the highs or lows of the two previous bars, a device meant to reduce cases where the dot closes in so fast that ordinary wobble on the very next bar touches it. Some programs apply this limit differently or use a variant that judges reversals on the close, so if the dots sit in different places from another chart, check the calculation method first.

How to read it: direction and stop level

There are two things to read in Parabolic SAR. One is the current direction, shown by which side of price the dots are on; the other is the stop level represented by the dot's position itself. Wilder designed the dot from the start to serve as a stop position. In an uptrend, the price at the dot becomes the level at which the bullish reading is given up, and since the dot rises every bar, that level rises with it. The gap between dot and price shows how much would be given up at that moment. Early in a trend the gap is wide, and as the trend lasts it narrows. So even within the same uptrend, one that just started and one that has run for a long time have different distances to the dot. This is also why many people pair it with ADX. Because the dots flip often when ADX is low and direction is unclear, they first use ADX to see whether the environment has a clear trend and then read the dots as stop levels within it. Reading the dot's position as support or resistance does not fit. That price is just a value the formula produced; it does not mean orders are gathered there.

Common misconceptions

Parabolic SAR looks simple with its single dots, but without knowing the reversal rule and the acceleration structure it is easy to misread. These are misconceptions that come up often.

• Thinking the close must cross the dot for a reversal (Wilder's definition uses the high and low)
• Treating the dot's position as support or resistance where orders are gathered
• Reading the dots closing in only as a sign of weakening price (they close in just from time passing)
• Treating every reversal as the start of a new trend
• Not matching settings and calculation method when the dots differ from another chart

How it looks different in crypto and stocks

Because Parabolic SAR reverses the moment the high or low touches the dot, markets with many long-wicked bars see more frequent reversals. Crypto trades around the clock, and short spikes are common in thin hours, so on short bars a single wick often flips the dots even while a trend continues. In stocks, news from the closed period appears as an opening gap the next day, and when a gap jumps right past the dot, trading starts at a much worse price than the SAR used as the reversal price. If you use the dot as a stop position, that position may not actually hold. Large Korean stocks such as Samsung Electronics and SK hynix have a daily price limit, so on days pushed to the limit you may not be able to trade as much as you want, and for US indexes and large tech stocks, whatever moved in extended hours appears as a gap in regular-session bars. Also, the acceleration factor grows with the number of new highs or lows, not the size of price moves, so the same settings make the dots close in quite differently on low-volatility large caps and high-volatility coins.

Reading it on a live chart

Under Wilder's definition, the current bar's SAR is already fixed by information up to the previous bar, so on a forming bar the dot usually does not move. What moves is the bar's high and low, and the moment either touches the dot, a reversal occurs and the dot jumps to the other side. A bar's high and low only widen before the close and never retreat, so under this definition a reversal that happened on a forming bar rarely disappears by the close. That sets it apart from other trailing lines judged on the close, which can flip and flip back before the bar ends. On the other hand, the next bar's SAR keeps changing depending on whether the forming bar makes a new extreme point, so where the next dot lands is settled at the close. If a program uses a variant that judges reversals on the close, a reversal on the forming bar can disappear again, so first check which method the tool you are viewing uses. When live data drops and reconnects, wicks from missed bars may be filled in later, making the reversal timing look different.

A practical checklist

When looking at Parabolic SAR, checking in the order below reduces the mistake of leaving judgment to a single dot. Recheck the reading on closed bars.

• Check the acceleration start, step and maximum, and the bar length
• Check whether reversals are judged on the high and low or on the close
• Read the current direction from which side of price the dots are on
• Use the gap between dots and price to gauge how far the trend has run
• Separately check with ADX or a higher bar length whether the environment has a clear trend
• For instruments that gap often, allow for the dot not holding as an actual stop price

Limits and disclaimer

Parabolic SAR always points either up or down, so it produces a direction even in stretches that have none. Following its reversals in a range tends to mean repeatedly confirming bullish flips near the top and bearish flips near the bottom. This is a weakness shared by trend-following indicators, and the acceleration structure makes it especially pronounced here. Looking back over one long trend, the dots seem to have followed it well, but the full picture appears only when the frequent reversals in the ranges along the way are included. This article did not measure performance after reversals, and it can vary widely by instrument, bar length and settings. This site has no dedicated Parabolic SAR tool; a similar trailing line that follows price can be seen in the Supertrend scanner. This article only explains the indicator's definition and how to read it, and does not recommend any trade. Actual decisions and their results are your own.